COMMUNICATIONS IN NUMERICAL METHODS IN ENGINEERING Commun. Numer. Meth. Engng 2000; 00:1–6 Prepared using cnmauth.cls [Version: 2002/09/18 v1.02] Signiﬁcance of Equal Principal Stretches in Computational Hyperelasticity Boris Jeremi´ c and Zhao Cheng Department of Civil and Environmental Engineering, University of California, Davis, CA, 95616, U.S.A. Vol. 21, Issue 9, pp 477-486, September 2005 SUMMARY The computational signiﬁcance of the case of two or three equal principal stretches in large deformation analysis is investigated in this paper. A detailed analytical study shows that the previously suggested solutions, based on numerical perturbations, are not adequate and might lead to erroneous results. A number of examples are presented to illustrate the approach. Copyright c  2000 John Wiley & Sons, Ltd. * Correspondence to: Boris Jeremi´ c, Department of Civil and Environmental Engineering, One Shields Ave., University of California, Davis, CA, 95616, U.S.A. jeremic@ucdavis.edu Contract/grant sponsor: NSF–PEER ; NSF; contract/grant number: EEC-9701568; CMS-0337811 Copyright c  2000 John Wiley & Sons, Ltd.